The overall objective of the proposed project is to elucidate the role of taurine and gamma-aminobutyric acid (GABA) in mammalian retina. More specifically, we plan to perform the following studies: 1. To identify GABA-containing and taurine-containing neurons and their pathways in retina by localizing their respective synthesizing enzymes, namely, L-glutamic acid decarboxylase (GAD) for GABA and cysteinesulfinic acid decarboxylase (CSAD) for taurine using immunocytochemical methods with specific anti-GAD and anti-CSAD sera, respectively. 2. To delineate the mechanism by which the levels of GABA and taurine in various retinal cell types are maintained. The high affinity and low affinity uptake of taurine and GABA, the activities of CSAD and GAD and the concentration of taurine and GABA will be determined in isolated cells and in various cellular and subcellular fractions so that the role of uptake and enzymatic synthesis in maintaining the steady-state levels of these amino acids can be elucidated. 3. To localize GABA and taurine high affinity uptake systems in retina using a combination of light and electron microscopic autoradiographies. 4. To elucidate the role of taurine and GABA in the development of retinal function. The concentration of taurine and GABA and their respective uptake systems and the activities and the quantities of their respective synthesizing enzymes, CSAD and GAD, will be measured at various stages of developments with special emphasis around the time of active synaptogenesis. In addition to the normal conditions, animals with photoreceptor dystrophy or animals treated with either taurine-free diet, monosodium glutamate, or iodoacetate-L-malic acid mixture will also be examined. Immunocytochemical techniques will also be used to localize CSAD and GAD, so that the migration and arrangement of taurine-containing and GABAergic neurons can be traced during development.